Dynamic Analysis Of Predation System Under Food Web Structure

Because more and more species are endangered,or even in danger of extinction,so the study of factors affecting biodiversity is imminent.On the species diversity in the influence factors of forming,Allee effect and habitat loss play an important role.The Allee effect greatly increases the risk of local or even global extinction of species,especially for those with low population density,and habitat loss is an important cause of the declining species diversity.Therefore,this paper focuses on the effects of these two factors on species diversity.This paper is divided into two parts: the first part is the spatiotemporal dynamic analysis of the predator-competition system with Allee effect;the second part is the comparison of the effects of two kinds of habitat loss on the community structure of complex food web.In chapter 1,the introduction part,mainly introduces the Allee effect,food web model,habitat loss model,the cellular automata model and the research significance of this study.In chapter 2,focuses on constructing a kind of predator-competition system with Allee effect.Through analyzing the stability of the system and the dynamic analysis of time and space,aims to explore the Allee effect on the system,the influence of which provide theoretical basis for biodiversity protection,helps people to deepen understanding of the ecological system stability and improve the awareness to protect the species.The results show that the damped oscillation of the system caused by the Allee effect of the predator is not conducive to the stability of the predator-competitor system,the increase of Allee effect threshold leads to the decrease of predator population density and the increase of prey population density,and the initial population size of the predator has a significant effect on the system.When the initial value is large,the system finally reaches stability.When the initial value is small,the system produces chaos.Systems with Allee effect are more likely to produce an aggregate distribution pattern in space.This result to some extent complements the previous conclusion.In chapter 3,based on the niche model,a complex food web structure with four levels of nutrients is constructed.A stable ecosystem is obtained according to the evolutionary rules of the food web,then random habitat loss and spread habitat loss were added to the system.The spatial distribution of habitat loss was only affected by two different habitat loss modes,among which the available habitats of random habitat loss presented the discrete form of dot lattice,while the available habitats of spreading habitat loss presented the form of patch aggregation.Through the contrast research,designed to show that different patterns of habitat loss affect the stability of a complex food web structure.The results showed that the number of damaged habitats increased,resulting in an increase in the proportion of empty patches and an overall decline in species diversity with the aggravation of habitat loss,random habitat loss leads to a higher number of empty patches than diffuse habitat loss,and random habitat loss leads to continuous fluctuations in the number of species in the food web,while extensive habitat loss leads to a continuous decline in the number of species in the food web,thus causing greater harm to species diversity.In chapter 4,summary of the main results of this paper,and the future research direction.The results of this paper will help researchers to further understand how the Allee effect and habitat loss affect the extinction of species,thus providing a theoretical basis for the research on the maintenance of species diversity.